Energy management

The makings of the microgrid

Microgrids are spreading globally, driven by technological, regulatory, economic, and environmental factors. Siemens helps build and get the best from these modern energy systems.

To a greater or lesser extent, every business needs access to reliable and economical sources of power. It is an additional bonus for some if that electricity can be generated using renewable sources. Modern technology allows businesses to meet these needs themselves, producing energy as well as con­suming it locally, creating flexible networks known as “microgrids.”
At the dawn of the electrical age, every grid was a microgrid – a locally limited system in which power was generated and distributed to users. Gradually these were subsumed into larger networks, becoming national or even crossing frontiers. Economy of scale dictated ever larger, usually fossil-fuelled generation plants, supplying often distant cities and industrial centers via transmission at high voltage.
But now the trend has reversed toward generation that is again decentralized, potentially renewably sourced, and often within flexible modern microgrids, able to attach or disconnect from the wider system at will. Microgrid operators can take advantage of management systems able to tell them exactly when it makes sense to generate, when to draw power, and when to sell power to the local utility company. Businesses of various size, whether they use less than 1 or more than 100 MW, are evolving from being passive consumers to becoming active (if assisted) “prosumers.”

Higher efficiency

Different reasons are driving this development across varied environments and customer groups. In Europe, regulated tariffs have risen and subsidies are offered for sales to national grids from renewable sources. This has led, for example, to more than one in six companies in Germany generating their own power. Technology has also assisted, with solar, wind, and gas turbine generation becoming ever cheaper, as has battery/hydrogen storage – all allowing insulation from the uncertainty of future utility tariffs. Microgrids’ low voltage distribution achieves less losses than the transmission network, boosting efficiency further still.
For some users, cutting CO2 emissions is also a goal, like the University of Genoa in Savona, Italy, where Siemens helped shape a microgrid based on solar power and micro-gas turbines. The Savona microgrid delivers 250 kW of power and 300 kW of heating for its 40,000 students, and this is viewed as a pilot for an ­expanded version for the surrounding green-minded city. Such combined heat and power (CHP) or combined cooling, heat, and power (CCHP) features are a common way to achieve still greater efficiency within microgrids.

Flexibility that can be relied on

In the booming US market, demand is driven more by reliability issues. Hurricane Sandy in 2012 left many New Yorkers without power for two weeks, a reminder that a big grid is not necessarily a safe one – and concerns relate to malicious attacks as well as natural disasters. Microgrids enjoy the option to disconnect temporarily from the main grid if outages threaten, or indeed can remain permanently as separate “islands.” At the same time, if its own generation were to fail, a connected microgrid has the option of drawing on the main grid as backup.
Major industrial endeavours, such as mines and chemical plants in Latin America for example, are attracted by cost reduction, as electricity can account for a tenth of the value of mined commodities. But they are also drawn by microgrids’ “power quality,” voltage, and frequency levels that will not vary because of wider system disturbance.

Microgrid-Management

Siemens Digital Grid

Siemens Digital Grid delivers a range of software and services to help microgrids achieve these benefits, each modular and scalable according to customer needs. The SICAM Microgrid automated control system can check the status of local assets and the wider grid, using a rule-based algorithm to connect or disconnect. The more complex Spectrum SP7 MGMS management system can also take account of future load and weather forecasts to optimize in real time the energy dispatch and can interact with wholesale power markets to maximize economic return or minimize CO2 emission over a longer term.
Naturally, linkage with the power system hardware and integration of equipment from other Siemens’ divisions is smooth. In another project, residential customers in a district in Bristol, UK, were supplied with SoLa energy storage linked to rooftop PV panels. This increased the microgrid’s resilience, cut costs, and delivered greater efficiency. In the next phase, Siemens will also work with largescale buildings to optimize energy efficiency.
Constantin Ginet, Siemens’ head of Microgrids global unit, explains that “we can demonstrate to our customers what their payback will be, and therefore what is the added value of having a microgrid.” He stresses the importance of understanding the as-is situation of a potential customer before laying out future scenarios. If they decide to develop a microgrid, customers can also choose between making their own capital investment or taking advantage of Siemens’ experience in financing models. Constantin Ginet sums up: “Our offering, made up of consulting, core microgrid products such as control systems and storage, access to partners, and financing models is a complete solution to the market.” As this rapidly expanding market segment testifies, Siemens is on trend with microgrids.